From Greenlivingpedia, a wiki on green living, building and energy

350 is the most important number on the planet. We are building an international movement to spread that number, engage our leaders and take action on climate change. Join Us.

350 is the number leading scientists say is the safe upper limit for carbon dioxide--measured in "Parts Per Million" in our atmosphere. 350 PPM - it's the number humanity needs to get back to as soon as possible to avoid runaway climate change.

On October 24 2009, we will stand together as one planet and call for a fair global climate treaty. United by a common call to action, we'll make it clear: the world needs an international plan that meets the latest science and gets us back to safety.